Previously known such lighting fixtures comprise a single top reflector plate usually having the same curvature over its entire width and being placed in the space between the two side reflector plates. Such fixtures offer the advantage that they utilize a comparatively large proportion, up to 80%, of the total quantity of light radiated from the fluorescent lamps, and further they ensure a relatively even illumination of the surface situated under the fixture and illuminated thereby.
It should be noted that the terms of direction such as "upwards", "downwards", "perpendicularly" and "horizontally" are used here and in the following on the assumption that the fixture, as is normally the case, is mounted with the axes of the fluorescent lamps situated in the same horizontal plane and with the light emission opening pointing downwards, even though the fixture in special applications can be oriented differently so that by these applications said terms of direction do not agree with reality.
A further advantage of the known fixtures of said type is that as a result of the transverse reflector plates, whether smooth or more appropriately having an almost serrated cross-section, they do not seem glaring even when viewed obliquely in a direction directly towards the fluorescent lamps and even if the light emission opening is not covered by a light diffusion plate.
Less convenient it is, however that in the known fixtures of the type concerned, the parts of which are normally made from plastic and, for achieving the reflector effect, metallized either on the inner side (side and top reflector plates) or on both sides (transverse reflector plates), a number of differently shaped and dimensioned parts are used each requiring expensive manufacturing machines and moulds, and the assembling of which requires specially trained persons since the parts must match perfectly.
Hitherto, therefore, such fixtures have been manufactured centrally and then been distributed to middlemen who have e.g. mounted the sockets for the fluorescent lamps and distributed the fixtures to electricians. As a result of the small weight, but large volume of the fixtures, the transport costs have relatively been too heavy.